The invention relates to improvements in methods of and in apparatus for manipulating webs of photosensitive material. More particularly, the invention relates to improvements in methods of and in apparatus for manipulating webs (e.g., exposed or exposed and developed photographic films or webs of photographic paper) whose trailing ends are spliced or otherwise affixed to leaders of elongated flexible strips of paper, plastic or the like and wherein the trailing end of the strip is connected to a carrier, e.g., to a core which is rotatably mounted in a cassette or another suitable housing or support and serves as a means for storing a supply of convoluted web and strip.
Photographic laboratories which are designed to process large numbers of customer films per unit of time are normally equipped with devices (such as suitable splicers) which join a large number of exposed but undeveloped customer films end-to-end in order to form an elongated composite web which is convoluted onto a core and is stored in a light-tight cassette or another housing or receptacle. A cassette which contains a composite web consisting of a large number of customer films is then transferred to an optimum position for admission of successive films of the composite web directly into a developing machine. It is further customary to ensure that the films which happen to be in the process of advancing through the baths and other stations of the developing machine will not come to a halt when the supply of interconnected films in a cassette is exhausted. This could result in damage to or in total destruction of one or more films which are confined in the baths of the developing machine while the emptied cassette is being replaced with a fresh (filled) cassette and the leader of the foremost film in the fresh cassette is being spliced to the trailing end of the last film which has been withdrawn from the emptied cassette. Proposals to avoid damage to exposed films in the developing machine include the provision of a magazine which is located upstream of the inlet of the developing machine and stores a reasonable supply of exposed film for transport into and through the developing machine while the last or rearmost film of such supply is being spliced to the foremost film of a composite web in the fresh cassette.
As a rule, the capacity of the magazine upstream of the developing machine is relatively small in order to save space and for certain other reasons (such as accessibility of the inlet of the developing machine). Therefore, it is necessary to carry out the splicing operation with little loss in time. An important prerequisite for shortening the interval which is required to complete a splicing operation is to rapidly detect the trailing end of the last film of a preceding composite web for proper positioning preparatory to splicing of such trailing end to the leader of the foremost film of the next-following composite web. This renders it possible to reduce the capacity of the magazine as well as to accurately position the detected trailing end at the splicing station for attachment to the leader of the foremost film of the next composite web.
Attempts to locate the trailing end of the last film of a composite web which is being unwound from a core or spool in the interior of a cassette include the provision of means for monitoring the rotary movement of the core or spool in a cassette for a composite web of interconnected exposed photographic customer films. Signals denoting the angular position of the core were to be processed in order to ascertain the location of the trailing end of the last film of the composite web. Such proposal has failed to find acceptance in the relevant industry because the trailing end of the last film could not be detected with a requisite degree of accuracy. One of the reasons is that the trailing end of the last film of a web consisting of a plurality of spliced-together customer films is likely to become separated from the core or spool while the latter is still surrounded by one, two or more convolutions of the last film.
In accordance with another presently known proposal, the developing machine is provided or combined with apparatus for continuously monitoring a marginal portion of a composite web of spliced together exposed photographic films which are in the process of entering the first bath (normally a developing bath) in a developing machine. Such apparatus render it possible to accurately detect the trailing end of the last or rearmost film of a web; however, each such apparatus is capable of monitoring only one specific format or type of exposed films. Thus, it is necessary to furnish the developing machine with two or more discrete monitoring apparatus, one for each popular type or format of customer films. Proper monitoring of successive composite webs consisting of photographic films having different sizes in accordance with the just outlined proposal is possible only if the web is monitored in the middle between its marginal portions. This will invariably result in damage to or even complete destruction of a large number of exposed but undeveloped customer films, a situation which is unacceptable to the owners of photographic processing laboratories.